MSVC buildfarm critters are not running modules' TAP tests

I noticed $subject while checking to see if commit db4383189's
new test script was behaving properly in the buildfarm. dory,
for one, should be running it but it just isn't.

It looks to me like the reason is that src/tools/msvc/vcregress.pl's
subroutine subdircheck isn't considering the possibility that
subdirectories of src/test/modules contain TAP tests. The
same code is used for contrib, so several existing TAP tests
are being missed there too.

I took a stab at fixing this, but lacking a Windows environment
to test in, I can't be sure if it works. The attached does kinda
sorta work if I run it in a Linux environment --- but I found that
system() doesn't automatically expand "t/*.pl" on Linux. Is that
an expected difference between Linux and Windows perl? I hacked
around that by adding a glob() call in sub tap_check, as seen in
the first hunk below, but I'm not very sure if that hunk should
get committed or not.

For ease of review, I did not re-indent the main part of sub
subdircheck, though that needs to be done before committing.

Anybody with suitable tools care to test/commit this?

regards, tom lane